A known instrument Provided with auxiliary means for facilitating the setting out of boundaries is described and illustrated in U.S. Pat. No. 4,560,270. This instrument incorporates a one-way sound transmitting facility, by means of which audible instructions can be sent from the measuring instrument to the prism carrier. This facility enables the instrument operator to verbally direct the prism carrier to the desired boundary mark or setting out location. This instrument is also provided with a line sighting instrument which is mounted in a fixed position in relation to the electronic distance gauge although not connected electronically thereto, and which emits two slightly diverging light beams of mutually different character. The two light beams overlap one another in a relatively narrow central zone.
This instrument includes a minicomputer into which there is fed data concerning the setting-out points or boundary line settings or area boundary settings for the region to be set-out or staked. If the boundary is to be marked or set out in point form, the instrument operator feeds into the computer the point number of each boundary marking point concerned. An indicator then displays data concerning these setting-out points in relation to the instrument, e.g., such data as horizontal angle settings, horizontal distances and possibly also vertical distances, these settings and distances being calculated by the computer subsequent to carrying out the aforesaid measurements against a reference point. The operator then adjusts the setting of the instrument to the given horizontal angle setting. The prism is then moved by the assistant to a point on the plot at which the two light beams transmitted from the direction indicating unit of the instrument overlap one another and at which the prism on the setting-out rod is in alignment with the measuring instrument. The instrument continuously measures the distance to the prism and the gradient of the electronic distance meter (EDM). The horizontal distance is calculated and presented on the indicator. The instrument operator instructs the assistant carrying the prism to move closer to or further away from the instrument until the distance shown coincides with the distance given for the setting-out point in question. Although the work of staking out boundary points can be effected relatively smoothly with this known instrument, it requires that the two persons concrned be able to communicate with one another.